/*
 * Licensed to the Apache Software Foundation (ASF) under one or more
 * contributor license agreements.  See the NOTICE file distributed with
 * this work for additional information regarding copyright ownership.
 * The ASF licenses this file to You under the Apache License, Version 2.0
 * (the "License"); you may not use this file except in compliance with
 * the License.  You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */
package com.sondertara.common.bean.expression;

import com.sondertara.common.bean.PropertyUtilsBean;

/**
 * Property Name Expression Resolver.
 * <p>
 * Methods such as PropertyUtilsBean's <code>setNestedProperty()</code> method
 * use a <code>Resolver</code> to process a <i>property name</i> expression and
 * resolve <i>nested</i>, <i>indexed</i> and <i>mapped</i> property names. The
 * following code provides an example usage demonstrating all the methods:
 *
 * <pre>
 * // Iterate through a nested property expression
 * while (resolver.hasNested(name)) {
 *
 * 	// isolate a single property from a nested expresion
 * 	String next = resolver.next(name);
 *
 * 	// Process...
 * 	String property = resolver.getProperty(next);
 * 	if (resolver.isIndexed(next)) {
 *
 * 		int index = resolver.getIndex(next);
 * 		bean = getIndexedProperty(bean, property, index);
 *
 * 	} else if (resolver.isMapped(next)) {
 *
 * 		String key = resolver.getKey(next);
 * 		bean = getMappedProperty(bean, property, key);
 *
 * 	} else {
 *
 * 		bean = getSimpleProperty(bean, property);
 *
 * 	}
 *
 * 	// remove the processed property from the expression
 * 	name = resolver.remove(name);
 * }
 * </pre>
 *
 * In order to create an implementation, it is important to understand how
 * BeanUtils/PropertyUtils uses the <code>resolver</code>. The following are the
 * main methods that use it:
 * <ul>
 * <li>{@link PropertyUtilsBean}
 * <ul>
 * <li>{@link PropertyUtilsBean#getIndexedProperty(Object, String)}</li>
 * <li>{@link PropertyUtilsBean#getMappedProperty(Object, String)}</li>
 * <li>{@link PropertyUtilsBean#getNestedProperty(Object, String)}</li>
 * <li>{@link PropertyUtilsBean#getPropertyDescriptor(Object, String)}</li>
 * <li>{@link PropertyUtilsBean#getSimpleProperty(Object, String)}</li>
 * <li>{@link PropertyUtilsBean#setIndexedProperty(Object, String, Object)}</li>
 * <li>{@link PropertyUtilsBean#setMappedProperty(Object, String, Object)}</li>
 * <li>{@link PropertyUtilsBean#setNestedProperty(Object, String, Object)}</li>
 * <li>{@link PropertyUtilsBean#setSimpleProperty(Object, String, Object)}</li>
 * </ul>
 * </li>
 * </ul>
 *
 * @version $Id$
 * @see PropertyUtilsBean#setResolver(Resolver)
 * @since 1.8.0
 */
public interface Resolver {

  /**
   * Extract the index value from the property expression or -1.
   *
   * @param expression
   *            The property expression
   * @return The index value or -1 if the property is not indexed
   * @throws IllegalArgumentException
   *             If the indexed property is illegally formed or has an invalid
   *             (non-numeric) value
   */
  int getIndex(String expression);

  /**
   * Extract the map key from the property expression or <code>null</code>.
   *
   * @param expression
   *            The property expression
   * @return The index value
   * @throws IllegalArgumentException
   *             If the mapped property is illegally formed
   */
  String getKey(String expression);

  /**
   * Return the property name from the property expression.
   *
   * @param expression
   *            The property expression
   * @return The property name
   */
  String getProperty(String expression);

  /**
   * Indicates whether or not the expression contains nested property
   * expressions or not.
   *
   * @param expression
   *            The property expression
   * @return The next property expression
   */
  boolean hasNested(String expression);

  /**
   * Indicate whether the expression is for an indexed property or not.
   *
   * @param expression
   *            The property expression
   * @return <code>true</code> if the expresion is indexed, otherwise
   *         <code>false</code>
   */
  boolean isIndexed(String expression);

  /**
   * Indicate whether the expression is for a mapped property or not.
   *
   * @param expression
   *            The property expression
   * @return <code>true</code> if the expresion is mapped, otherwise
   *         <code>false</code>
   */
  boolean isMapped(String expression);

  /**
   * Extract the next property expression from the current expression.
   *
   * @param expression
   *            The property expression
   * @return The next property expression
   */
  String next(String expression);

  /**
   * Remove the last property expresson from the current expression.
   *
   * @param expression
   *            The property expression
   * @return The new expression value, with first property expression removed
   *         - null if there are no more expressions
   */
  String remove(String expression);

}
